1. Field of the Invention
The present invention relates to a method for producing a pulley for a belt-type continuously variable transmission of an automobile or the like (a belt-type continuously variable transmission pulley).
2. Description of the Related Art
In the field of pulleys for belt-type continuously variable transmissions (hereinafter referred to as belt-type CVTs), for example, Japanese Laid-Open Patent Publication No. 2007-262470 is known as a conventional technology specifying a surface texture of a sliding surface on which a belt is slid.
In Japanese Laid-Open Patent Publication No. 2007-262470, a pulley is composed of a chrome steel or a chrome molybdenum steel according to JIS G4053. The sliding surface of the pulley contains a hardened layer harder than the inside, and has a surface texture with a surface roughness Rz of 1.4 to 6.3 μm and a ratio Rpk/Rvk (a ratio of the reduced peak height Rpk to the reduced valley depth Rvk according to JIS B0671) of less than 0.75.
The pulley having the above surface texture is excellent in abrasion resistance and is useful for the CVT.
In view of improving the abrasion resistance of the sliding surface, it is important to increase an oil holding property (an ability to hold a lubricant oil) of the sliding surface. This is described also in Japanese Laid-Open Patent Publication No. 2007-262470. In this patent publication, the surface texture of the sliding surface is defined based on the surface roughness Rz, the reduced peak height Rpk, and the reduced valley depth Rvk, and it is particularly preferred that the reduced valley depth Rvk is larger than the reduced peak height Rpk.
However, even when the reduced valley depth is larger than the reduced peak height, a lubricant oil cannot be easily introduced into a valley with a sharp shape. On the contrary, when the valley width is excessively larger than the peak width, the lubricant oil in the valley may readily leak therefrom. Thus, it may be difficult to hold the lubricant oil in the valley, so that the pulley cannot always have a desired oil holding property.